1. Field of the Invention
This invention relates to fiber optic telemetry systems. More particularly, the present invention pertains to an optically multiplexed sensor and coupler arrangement in a telemetry system for improved efficiency and reduced cost.
2. Description of the Prior Art
The fiber optic telemetry systems with which the present invention is concerned can be categorized in two general types or designs: The full-ladder and the half-ladder telemetry systems. While each one of these two conventional telemetry systems may be suitable for particular applications, none has proven to be completely satisfactory.
For illustration purposes, a conventional full-ladder telemetry system is shown in FIG. 1. As will be explained later in greater detail, while the full-ladder telemetry system presents a relatively acceptable throughput level, it suffers from several drawbacks. In this regard, each interferometer or sensor in the full-ladder telemetry system requires two couplers, one coupler for splitting the input signal, and another output coupler for combining the split signal. Furthermore, the full-ladder telemetry system requires a relatively large amount of optical fibers and a relatively large number of splices in order to interconnect the constituent components. Thus, the increased number of the components in the full-ladder telemetry system increases its cost and limits its application.
For illustration purposes, a conventional half-ladder telemetry system is shown in FIG. 2. As will be explained later in greater detail, while the half-ladder telemetry system provides a relatively efficient distribution among its sensors, its throughput is substantially low. Thus, the conventional half-ladder telemetry system is severely limited as to the number of constituent sensors or interferometers in that an increase in the number of sensors can reduce the throughput signal to an undesirably low level.
Therefore, it would be highly desirable to have a new and improved sensor and coupler arrangement in a telemetry system for improved efficiency and reduced cost.